So while we are on the topic of electrical, I figure I'll post this tool that I use a lot when messing around with my Xterra. Beware, this one might get a bit long, because it's hard to talk about it in three sentences or less. And since I'm in quarantine for a few days with nothing better to do, and I'm going absolutely stir crazy over it (and happened to be checking out an issue on the wife-mobile anyway), here we are.
So it's the
Power Probe III. Mind you, there are newer versions of this thing, but they are as yet a bit more expensive for what they are, and this one does about everything I need it to do without needing to drag my Fluke 87V out of the work truck.
So what you get with this little guy are a few really handy things that you can use. First off, it's a voltmeter. A red light with the battery voltage indicates it is checking the voltage, and you don't need to push a button to do it. That's kind of handy. You can also set it to remember the voltage so you can take a reading on something in a tight place, say under a dash, and you can pull the probe back and look at the display, which is actually what the first picture is.
To check for ground, you simply touch the probe against something grounded to the battery, like say the battery terminal. A lot of problems can be sourced back to a bad ground, and if the light doesn't come on, you know you don't have a solid ground connection. Additionally, as you can see from the picture, it shows 0.0 which is an ohm check. 0 ohms means good continuity.
I should also point out that you can set it to beep when you touch things with it. Anything with good ground connection or continuity will have a low tone beep, and anything with voltage being sent to it will have a higher pitch beep.
You can also check your battery voltage with the meter floating (the probe not touching anything) by pressing the upper + side of the switch. You can do this because the cable that the probe is connected to connects to the positive and negative battery terminals.
Example of use:
Okay, so let's say the power inverter isn't working on my Xterra. I've already determined that there is no voltage to the cable connection at the inverter itself by probing it, and nothing came up. I know that I have a cable connection at the battery, an inline mega fuse, and the inverter itself. Between the fuse and the inverter is about 12 feet of cable running under the Xterra to the back where it penetrates the cab. Well, being as I checked voltage at the B+ connection point at the inverter, I need to work backward to the voltage source. However, I also need to establish that the battery actually has voltage, so what I always do is start at the source of the voltage and work my way to the component.
So step 1: Check voltage at the source. We can do that by pressing the + side of the switch, and it reads battery voltage because I have my power cables connected right to the battery. Easy enough.
Step 2: Now check the terminal connection point. I always check the copper connector on the cable because if there is a bad connection, I won't see any voltage. So far so good according to this picture.
Step 3: Check voltage on the battery side of the fuse connection. If there is voltage, you know your cable from the battery is good.
Step 4: Check voltage on the inverter side of the fuse. If you have battery voltage there, you can safely say your cable and fuse up to that point are good. So if there is no voltage at the connection on the inverter, the problem must be the cable somewhere down the line. Now the hard work of finding the break in the wire is next.
Now, that's also a quick and dirty way to check a fuse. If you have voltage on both sides of a fuse, it's probably good. If you have voltage on one side, but not the other, the fuse probably isn't good. However, the most proper way to check a fuse is to pull it and continuity check it. The meter has you covered because it also has a little ground clamp that comes out of the bottom for just such a thing as component bench testing.
A green light with 0.0 indicates that this fuse is good. Remember, that's 0.0 ohms of resistance between those two connection points on the fuse. And no buttons need to be pressed for this operation.
So let's say you fixed your problem in the cable. You either found a break in it or determined that the ground side connections were bad by doing continuity checks all the way back to the negative terminal on the battery. Whatever the case is, you identified the problem and fixed it. But you should always check. So leaving the the probe's power cables connected to the battery, you walk back and simply probe the positive cable on the inverter. Bam! 12.7 VDC. Fixed. And all you had to do was pull the protective sleeve back and tap it with the tip of that very sharp probe.
Here's another couple of pictures of a fuse. The first fuse is bad. So no continuity means no green light. The alligator clip I'm holding is the one that comes out of the bottom of the probe for component testing.
Green light means a good fuse.
A word of caution though: Don't press the + side of the switch when testing fuses. You could blow the fuse you're testing. How else do you think I was able to blow that fuse for the picture? Yup, it popped it. Now, the probe does have a breaker on it, and there are some tests you can do to check continuity where you push + part of the switch, but I don't like doing that. It puts stress on the breaker. But it's there if you really need it.
Now here's the part that sold me on it. Component testing. So I had a friend with an Xterra, and he thought his IPDM had taken a dump. Neither of his low beam headlights would work. The highs would work fine, but the low's were dead. So I asked him to bring it over because we could not only test to see if there was continuity in the headlights themselves, we could also test them. Now, I've tested plenty of components passively with an ohm check just to find out that the meter was being fooled. It's oftentimes baffling, but electricity does weird stuff, especially when coils heat up under load. So my buddy brings his Xterra over, with a new IPDM, and I immediately pull the bulbs out of the headlight housings. He had done the same thing at his house. The filaments looked fine, but the continuity check told the story. No continuity. When I pressed the + side of the switch, nothing happened on the lows. But the high beam side came on when I switched to that terminal! Replaced the headlight bulbs and all was right with the world.
This is my favorite feature.
Being able to bench test components off and on the vehicle without having to drag out of a bunch of other crap is so handy. You can literally be voltage checking down the line, find the component connector, and supply voltage to it (preferably when disconnected from the vehicle) and run the component. But I've hot tapped the windshield wiper motor on our Saturn, and checked relays by supplying voltage to the control side of it to turn on lights.
And getting back around to checking component connections, if disconnected something that isn't working, you can simply insert the probe into the vehicle side of the connector and see if you have voltage or ground. If you have it, there's a decent chance the problem is in the component. If not, you can start going through the harness to find the problem.
Now I won't lie to you and say this is the end all be all of meters. It is another tool in the tool box. And honestly, it took me a little getting used to it when I first bought it simply because I've been using Fluke digital multimeters ever since I started my career. And there are a few other features on the Power Probe, like being able to spot voltage fluctuations to determine if rectifiers are bad or not. I've not had to use that feature yet since my alternator works fine.
But the most common things I do when using a meter on my vehicle are voltage and continuity checks. And for that, this thing is great. The kit comes with the meter, a removable probe, and an attached cable long enough to get back to your vehicle's rear end. The case includes pigtails that allow you to connect to your battery directly, or to a 12 volt receptacle. It also has an extension cable. I can see that coming in handy if I had a trailer hooked up to my Xterra and was trying to figure out a lighting issue.
All in all, it's definitely worth looking into if you're in need of something to perform some basic tasks and checks. And the price isn't too bad, especially if you're on a budget.